And I'm David Greene. Good morning. In Mexico, public schools have been in session for more than a week, but at least two million students have yet to see the inside of a classroom. Tens of thousands of teachers are on strike and they've taken over Mexico City's already chaotic streets. They're angry about a set of reforms being debated in Congress. Here's NPR's Carrie Kahn.

CARRIE KAHN, BYLINE: In the past week, protesting teachers have erected a huge tent encampment in Mexico's City's expansive Zocalo Plaza, repeatedly closed down the main Reforma boulevard, chased lawmakers out of Congress, and in the boldest and most disruptive move, shut down the thoroughfare to the airport, forcing tourists and travelers to walk to terminals under police escort.

(SOUNDBITE OF SWEEPING)

KAHN: On a break from the near constant protests, several teachers sweep away the dirt in their encampment in the city's downtown plaza. Estela Aparecio Bautista from Oaxaca says she came to make sure lawmakers hear about the conditions in her school.

ESTELA APARECIO: (Speaking Spanish)

KAHN: She says the first thing her kids tell her every morning is they're hungry, they have no shoes, and no one has school supplies. Fellow third grade teacher Hector Lopez Cuevas, also from Oaxaca, says he's upset about a move to start evaluating teacher performance.

HECTOR LOPEZ CUEVAS: (Speaking Spanish)

KAHN: He says lawmakers are moving too quickly. He says one standardized test can't evaluate a teacher with ample resources in Mexico City in the same way as a teacher with nothing working in Oaxaca. The powerful union has long blocked moves to weed out bad teachers. The union holds power over most hiring decisions also.

It's common practice for teachers to buy and sell tenured positions. President Enrique Pena Nieto campaigned on reforming the system, which he insists is substandard and in dire need of modernization if the country is to prosper. Once in office he quickly moved to jail the union's long time leader on embezzlement charges.

Overhauling the education system is just one of many reforms the President has taken on. But commentator Sergio Sarmiento says Pena Nieto has yet to deal with opposition as intransigent as the teachers.

SERGIO SERMIENTO: This is the biggest challenge he has had.

KAHN: In particular, he says, the president has a formidable foe in the teachers now protesting in Mexico City, a radical group known as Section 22 of Oaxaca.

SERMIENTO: Section 22 of Oaxaca has actually had strikes every year for the past 33 years. And they do it because they know they can get away with it and they know that they can get additional money.

KAHN: In fact, the teachers still receive their paychecks while on strike, thanks to the governor of Oaxaca, a member of the opposition party. Mexico City's mayor, also a member of the opposition, has done little to deter the protesters. Sarmiento says every politician that has gone up again Section 22 ultimately gives in to their demands.

That's exactly what happened last week when union members blocked lawmakers from entering the congressional palace. They were forced to convene in a nearby convention center and ultimately postponed voting on the measure to evaluate teachers. Meanwhile, residents of Mexico City are losing patience.